Think of a Number Puzzles Worksheet

Maths tricks trick 6: Think of a number · Set 17 · 40 questions

The trick (Undo the steps): Going forwards: do the steps in order. Going backwards: start from the result and undo each step, last one first. Undo + with −, × with ÷, and doubling with halving.

1. 1.Magic trick! Think of 12. Double it, add 4, halve it, then take away 12. What number do you get?
2. 2.Think of 10. Multiply it by 5, then add 4. What number do you end with?
3. 3.I thought of a number, added 5 and then doubled it. I got 40. What was my number?
4. 4.I thought of a number, multiplied it by 5 and added 4. I got 49. What was my number?
5. 5.I thought of a number, added 3 and then doubled it. I got 34. What was my number?
6. 6.I thought of a number, added 9 and then doubled it. I got 38. What was my number?
7. 7.Think of 9. Multiply it by 4, then add 5. What number do you end with?
8. 8.Think of 12. Multiply it by 2, then add 9. What number do you end with?
9. 9.Magic trick! Think of 7. Double it, add 10, halve it, then take away 7. What number do you get?
10. 10.Magic trick! Think of 20. Double it, add 12, halve it, then take away 20. What number do you get?
11. 11.Magic trick! Think of 19. Double it, add 10, halve it, then take away 19. What number do you get?
12. 12.I thought of a number, multiplied it by 2 and added 7. I got 29. What was my number?
13. 13.I thought of a number, added 5 and then doubled it. I got 16. What was my number?
14. 14.I thought of a number, added 1 and then doubled it. I got 36. What was my number?
15. 15.Think of 2. Multiply it by 5, then add 7. What number do you end with?
16. 16.Think of 7. Multiply it by 2, then add 8. What number do you end with?
17. 17.I thought of a number, added 9 and then doubled it. I got 56. What was my number?
18. 18.Think of 15. Multiply it by 2, then add 3. What number do you end with?
19. 19.I thought of a number, multiplied it by 4 and added 2. I got 34. What was my number?
20. 20.I thought of a number, multiplied it by 5 and added 2. I got 22. What was my number?
21. 21.Think of 14. Multiply it by 4, then add 8. What number do you end with?
22. 22.I thought of a number, multiplied it by 4 and added 5. I got 33. What was my number?
23. 23.Magic trick! Think of 19. Double it, add 4, halve it, then take away 19. What number do you get?
24. 24.I thought of a number, added 3 and then doubled it. I got 22. What was my number?
25. 25.Think of 9. Multiply it by 2, then add 5. What number do you end with?
26. 26.Magic trick! Think of 2. Double it, add 6, halve it, then take away 2. What number do you get?
27. 27.I thought of a number, multiplied it by 5 and added 3. I got 18. What was my number?
28. 28.I thought of a number, added 1 and then doubled it. I got 42. What was my number?
29. 29.Magic trick! Think of 3. Double it, add 10, halve it, then take away 3. What number do you get?
30. 30.I thought of a number, added 9 and then doubled it. I got 34. What was my number?
31. 31.I thought of a number, multiplied it by 4 and added 6. I got 18. What was my number?
32. 32.Think of 3. Multiply it by 5, then add 6. What number do you end with?
33. 33.I thought of a number, added 3 and then doubled it. I got 12. What was my number?
34. 34.Magic trick! Think of 13. Double it, add 12, halve it, then take away 13. What number do you get?
35. 35.Magic trick! Think of 15. Double it, add 8, halve it, then take away 15. What number do you get?
36. 36.I thought of a number, added 2 and then doubled it. I got 44. What was my number?
37. 37.Magic trick! Think of 6. Double it, add 8, halve it, then take away 6. What number do you get?
38. 38.I thought of a number, added 1 and then doubled it. I got 16. What was my number?
39. 39.Magic trick! Think of 3. Double it, add 6, halve it, then take away 3. What number do you get?
40. 40.Magic trick! Think of 5. Double it, add 16, halve it, then take away 5. What number do you get?

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